An API on-line debugging method is disclosed. The method includes developers writing interface annotations using standard JavaDoc format specifications, and adding user-defined annotations to the APIimplementation code, scanning the project by using API formatting description generation tool, analyzing the annotation information of JavaDoc format and user-defined annotations of the code to form aunified API formatting description, and registering the information and the annotations to an API center; the API center being responsible for unified management of all API documents, analyzing API formatting description, generating unified API documents and Web pages and persisting them; users reading the API documents and debug and test the API in real time by accessing the corresponding Web page through the client or browser. The method of the invention can automatically generate API documents without extra work and configuration in the development process, manage the API documents througha unified management platform, and can carry out on-line debugging on different types of APIs, thereby effectively improving the interface development efficiency and the interface integration quality.